Double three high planetary mill

ABSTRACT

A planetary rolling mill with nonoverlapping rolling cycles, i.e. a pair of work rolls leaves contact with the strip before a succeeding pair of work rolls engages the strip, wherein torsional vibrations of the drive elements are minimized, in that torque stresses on the drive elements are relieved before the end of each rolling cycle, i.e. before each pair of work rolls leaves contact with the strip.

United States Patent Inventor Tadeusz Sen dzimir do '1. Sendzimir, lnc.P.O. Box 1350, Waterbury, Conn. 06720 Appl. No. 820,719

Filed May 1, 1969 Patented July 27, 1971 DOUBLE THREE HIGH PLANETARYMILL 14 Claims, 9 Drawing Figs.

lnt.Cl B2lb 21/00 Field of Search 72/224,

[56] References Cited- UNITED STATES PATENTS 2,960,894 1 1/1960 Platzer72/190 3,138,979 6/1964 Sendzimir 72/240 3,153,955 10/1964 Platzer72/190 Primary Examiner-Milton S. Mehr Attorney-Melville, Strasser,Foster & Hoffman ABSTRACT: A planetary rolling mill with nonoverlappingrolling cycles, i.e. a pair of work rolls leaves contact with the stripbefore a succeeding pair of work rolls engages the strip, whereintorsional vibrations of the drive elements are minimized, in that torquestresses on the drive elements are relieved before the end of eachrolling cycle, i.e. before each pair of work rolls leaves contact withthe strip.

PATENTED m2? i97| SHEET 1 UP 2 INVENTOR. 8 7ZDEusz SENDZ/M/f? MELV/LLE,Siva/45552, FOSTER A/VD HOFFMAN ATTORNEYS DOUBLE THREE HIGH PLANETARYMILL BRIEF SUMMARY OF THE INVENTION A. Background Planetary mills havingpowerful feeding means such as rolls which force a slab into the bite oftwo cooperating planetary assemblies at uniform speed are known. Suchmills are described, for example, in US. Pat. Nos. 2,710,550 and2,932,997.

In such mills the planetary assemblies are composed of a backing rollsurrounded by a plurality of spaced work rolls. Such mills are limited,so far as the choice of the number of work rolls is concerned, by theconsideration that there must always be a pair of work rolls in contactwith the workpiece, i.e. before each pair of work rolls leaves contactwith the strip the succeeding pair of work rolls must already be incontact with the slab. Thus, while the driving torque requirements willvary between two and one pair of work rolls they never fall to zero. Ifthis condition is not met, the entire driving mechanism includingspindles, pinions, and couplings, is subjected to dangerous anddestructive vibrations.

A driving spindle of a backing roll in some planetary mills willtransmit a torque of say 5,000 horse power at 200 r.p.m., and in sodoing is slightly twisted elastically like a torsion spring. All theother drive elements from the motor to the backing roll'arealso underelastic stress and unless a succeeding pair of rolls is also in contactwith the work, all this potential energy is suddenly released when thework roll leaves contact with the workpiece and the torque momentarilydrops nearly to zero. This recoil is very dangerous to the mill drivingelements.

B. Solution According to the present invention, by means of a mill ofgreat simplicity and ruggedness having large diameter work rolls andrelatively few working rolls, the problems above described are solved.Whereas a conventional planetary mill will be provided with 20 to 24work rolls per assembly, a mill according to the present invention canoperate with as few as two work rolls whereby only one pair of workrolls is ever in contact with the strip at any given time.

The present invention provides a method and means whereby the torquestresses on the drive elements are relieved before the end of eachrolling cycle, i.e. before each pair of work rolls leaves contact withthe strip.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a transverse cross-sectionalview of a mill accord ing to the invention.

FIG. 2 is a longitudinal cross-sectional view on the line Il-Il of FIG.ll.

FIG. 3 is a fragmentary schematic view ofa workpiece during reduction bya pair of work rolls.

FIG. 4 is a cross-sectional view on a greatly enlarged scale ofan edgeretaining roll and its mounting.

FIG. 5 is a schematic front elevational view of the mill and its drive.

FIG. 6 is a schematic side view of a torque compensating mechanism.

FIG. 7 is a schematic cross-sectional view of a modification oftheinvention.

FIG. 8 is a longitudinal cross-sectional view of another embodiment ofthe invention; and

FIG. 9 is a schematic cross-sectional view of the embodiment of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION The pair of coacting planetaryassemblies shown in FIGS. 1 and 2 consist of the two backing rolls 1 and1 each having as sociated therewith two work rolls 2, 2 and 3, 3'. Thebacking rolls l, I are mounted in chocks t, 4' and 5, 5' located inopenings in the mill housing 6.

While any suitable screw-down system may be employed the one illustratedhere provides that the outside peripheries of the chocks l, 4' and 5,5are eccentric with respect to the axis of the backing rolls so that theroll gap can be increased or decreased by rotating the chocks by acertain angle substantially as described in U.S. Pat. No. 3,138,979.

The path described by each work roll 2, 2' and 3, 3 around therespective backing rolls 1 and I is substantially circular; yet if thediameters of the work rolls with respect to the diameters of the backingrolls correspond to certain specific ratios and the speeds of rotationof the backing rolls and the cages 7,

7 which carry the work roll bearing chocks 7a, 7a are related in thesame ratio, then it will be clear that the angular positions of thebacking rolls 1, 1', when a work roll engages the workpiece and when itleaves the workpiece, will always be the same. The importance of thisresides in the fact that the backing roll instead of being cylindricalcan now be slightly profiled to cause the work roll to deviate from itscircular path and providing the substantial advantages which will beexplained in more detail hereinafter.

Any suitable means may be employed to drive the cages7, 7' in theappropriate ratio to the speed. of the backing rolls 1, 1. Preferably,for example, the cage 7 is driven from the backing roll 1, 1' through apair of gears 35, 36 and the cage 7' is similarly driven through anidentical pair of gears from the backing roll 1. The gears 35 and 36,best seen in FIGS. 2 and 8, are mounted on splines or bolted onto theirrespective shafts. They preferably have large teeth of suitable profileto permit variation in the center distance as necessitated by thescrewdown. Where larger adjustments in the center distance are desiredit is, of course, within the scope of the present invention to usevariable center mountings such as the well known Oldham couplings formounting the gears, or even to use intermediate gears. On larger millssuch a simple drive may not suffice to permit the full utilization ofroll diameters, and a suitable compensating drive may be employed.

Referring now to FIG. 3, the lower portion of this Figure shows the pathof a work roll 3 backed by a truly cylindrical backing roll, whereas theupper half shows the path of a work roll 2 when backed by a profiledbacking roll 1. In the lower half of the Figure it will be observed thatthe work roll 3 first contacts the slab 10 at the point A, and leavescontact just after passing the point D, which is the highest point ofits trajectory, where the slab 10 is already reduced to strip gauge 11.The orbiting velocity of the work roll 3 around the backing roll I, andtherefore the theoretical angular velocity of the cage 7, as the workroll 3 moves down the roll bite from the point A, to the point D,, isincreasing because the surface velocity of the workpiece increasesroughly in inverse ratio to the thickness of the workpiece. Thisprecession is very small; but as will readily be understood it tendsslightly to unload the potential energy stored in the spindles 9, 9 andthe driving mechanism of the mill because it causes the backing roll toturn faster than its drive before the moment when the torque demandsuddenly disappears as the work roll 3 leaves contact with the workpieceafter passing point D,.

But, if, as suggested above, advantage is taken of the fixedratio millgeometry, and if instead of using-a circular cross section backing roll1, the backing roll is given a slight profile, the roll 2 instead ofdescribing an are or a circle with its lowest point at D, may be causedto move along a straight line from C to D during the last part of itscontact with the workpiece and thus produces a parallel piece of strip11 instead of an arcuate one. As a result of this, not only is a betterproduct produced but it makes possible the unloading of a considerablylarger proportion of the elastic energy stored in the mill spindles.This is because the work roll 2 contacts the light gauge finished stripover a much longer distance, i.e. from the point C to the point D, andtherefor the precession of the work roll is much greater than if thebacking roll 1 were cylindrical.

If the part of the backing roll 1 corresponding to the entry of the workroll 2 into the roll bite, i.e. at the point A,, is also profiled, anadditional advantage is obtained in that a thicker slab such as it) canbe fed into the mill without exceeding the critical angle of entry ofthe roll 2 into the roll bite at A As is clearly explained in the twoUnited States patents above noted, an entry angle of about must not beexceeded. Above that angle the work roll 2 has a tendency to throw backa part of the surface layer of the workpiece, creating surface defectscalled back fins." It is clear that if the work roll 2 can be caused todeviate from its circular path, this angle of entry can be maintained,reduced or even rounded off, thus permitting considerably thicker slabsto be fed into the mill. This measure makes it possible to increase theratio between the thickness of the slab entering the mill at It) and thethickness of the strip leaving the mill at 11, whereby the precessionachieved between the points C and D is of still greater magnitude and inmost cases permits a reduction of the potential energy stored in thespindle and the drive mechanism at the end ofeach rolling cycle towithin tolerable limits.

In some cases, particularly in planetary mills of very largeproportions, the above described means for extending the precession ofthe work rolls ahead of their geometric angular positions are notsufficient. It is possible, however, to insert an independent element inthe driving means for positively controlling the angular position so asto eliminate considerably the dangerous shocks to the driving mechanism.Such an arrangement is shown in FIGS. 5 and 6. The driving motor 19drives the planetary mill 22 through a planetary reduction gear 23, apinion stand and flexible spindles 9, 9. In the planetary gear 23 (asbest seen in FIG. 6), the motor 19 is keyed to the central or sun pinion24 and the lower pinion of the pinion stand 20 is keyed to the satellitecarrier 25 of the planetary gear 23. Very precise and minute alterationsof the angular position of the work rolls 2, 2, 3, 3' at their point ofexit from the working cycle are produced by an angular movement of thering gear 26 of the planetary reduction gear 23. For this purpose thehousing of the ring gear 26 is provided with a lever 27 and a roller 28is mounted at the extremity of the lever 27. The roller 28 rides over acam 29 which rotates in a fixed angular relation to the rotation of theplanetary cages by any conventional driving means (not shown). Byproviding the cam 29 with a suitable profile, the required alteration ofthe angular position of the drive ends of the mill spindles can beachieved to coincide with a definite position of the work rolls 2, 2, 3,3, particularly the point at which the work rolls leave contact with theworkpiece, to insure that the elastically stored energy is relieved atthis point.

While the mill thus far described comprises planetary assemblies withtwo diametrically opposed work rolls, modifications are possible, andone of these is shown in FIG. 7 where each backing roll is provided withthree work rolls. The backing rolls have a diameter twice that of thework rolls. Since with a 2:1 ratio of diameters, the gear ratio fordriving the respective rolls is 3:l, it will be observed that only oneprofiled relief of the backing rolls is required to assure entry andexit of all three work rolls.

FIGS. 8 and 9 show a further modification wherein each backing roll hasfour work rolls, and the backing roll is four times the diameter of theworking roll. With a 4:1 ratio of diameters, a ratio between speeds ofthe backing rolls and the cages 7, of 25:1 is required. Thisconfiguration makes it possible to obtain twice the productionobtainable by a mill according to FIGS. land 2 without too great asacrifice in the rigidity of the cages, the importance ofwhich isexplained below.

The above-noted ratios are given as examples of possible diameter andspeed combinations. In some cases, for example, for softer metals it maybe advantageous to use even larger work rolls in relation to the backingrolls, such as work rolls of the same diameter as the backing rolls.With such an arrangement, it is possible to use six work rolls withthree profiles on the backing roll, or four work rolls in each cage withonly one profile on the backing roll. In the latter case, the other workrolls coact with the backing roll in supporting that particular workroll, which is in the roll bite, against deflection.

A mill according to the present invention having composite cagesrequires that the right and left cages be rigidly joined together toform one body which is rigid as to torsional as well as to bendingstresses. Torsional rigidity is essential since driving torque can beapplied conveniently at one end only, while the cage applies the driveto the work roll chocks 7a, 7a, which must stay parallel.

The cage 7 is a tubular body, the diameter of which is usually somewhatreduced at the two ends where the main chock bearings 4, 5 are located.In the embodiment of FIGS. 1 and 2, the cage is split for assemblyreasons and the two halves are tightly held together by the bearings 30and spacers 31 which are shrunk into them.

In the embodiment of FIGS. 8 and 9, each cage is a onepiece body. Theassembly of the cage over the backing roll 1 is made possible byshrinking bushings 32 of bronze or other suitable material upon thebacking roll necks so that the outer periphery thereof acts as a bearingsurface.

The provision of rigid cages 7 as described herein makes possible otherbenefits which could not be foreseen. l. The rigid cages can be used asrotary housings on which to mount small edge retaining rolls 33, 33which contact the upper and lower edge corners of the workpiecerespectively. One of the big problems connected with-planetary mills isside spreading of the workpiece, which finally results in a strip withedge cracks and reduced gauge in the edge area. The provision of theedge retaining rolls 33, 33, which press upon the protruding edgecorners after the passage of each work roll 2, effectively stops theprogress of side spreading, so that even materials having littleductility can be rolled successfully from a slab down to strip gaugeswithout sidecracks.

Since these edge retaining rolls 33 and 33' protrude beyond the plane ofsymmetry of the mill, they are disposed in such manner that the rolls 33and the rolls 33 never meet. Corresponding to the positions of the rolls33 there are provided the cavities 37 in the cage 7 and the cavities 37in the cage 7, whereby interference is avoided (FIG. 1). Adjustment forstrip width is provided, as best seen in FIG. 4, by the eccentrictrunnion 39 upon which the roll 33 is mounted; and the angular positionis maintained by engaging a pin 40 in a suitable slot in the flange 38.Since this adjustment has quite a narrow range, several pairs ofrecesses 37 are provided for the flanges 38 to take care of the wholerange of widths to be rolled on a given mill. 2. The usefulness of themill can be extended in that the cages 7 can be stopped and their drivedisconnected and the whole rnill can then be used as a four-high mill,where the work rolls 2 and 3 are both driven, and supported by thebacking rolls ll, 1. When used in this manner as a four-high mill, therolls 2, 3 may have a rough finish and the other rolls 2', 3' a finefinish for use in a finishing pass or passes. To switch from a roughingto a finishing pass it is only necessary to turn the cages 7, 7'

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. The method of reducing vibrations in the operation of a planetarymill having rotating driven backing rolls and work rolls mounted incages, which includes the step of intermittently varying the angularvelocity of the driving means for said backing rolls in timed relationto the working cycle of the said work rolls, so as to reduce stresses insaid driving means near the end of each rolling cycle.

2. The method of claim 1, wherein said variations in angular velocityare produced by causing said work rolls to deviate from their circularpaths and to move parallel to each other during the final portion of theworking cycle.

3. The method according to claim 2, wherein the deviation is produced bydriving the said roll cages at such a speed ratio with respect to thebacking rolls that each work roll, during its operating cycle, is backedby the same are of the circumference of the backing roll, and profilingsaid are to produce the required deviation.

4. The method according to claim 3, wherein said work rolls are alsocaused to deviate from their circular paths near their point ofengagement with the workpiece, to reduce the angle at which the workrolls meet the workpiece.

5. The method according to claim 1, wherein said variation in angularvelocity is produced by retarding the driving ends of the spindlesduring said last portion of the working cycle.

6. The method according to claim 5, wherein said variation is producedby driving said backing rolls through a planetary reduction gear havinga free element to oscillate in synchronism with the working cycles ofthe mill, so as further to relieve spindle stresses by retarding thedriving ends of said spindles in relation to their driven ends near theend of each working cycle.

7. A planetary rolling mill having a pair of backing rolls, and a numberof work rolls symmetrically associated with each backing roll, thenumber of work rolls associated with each backing roll being such that agiven pair of work rolls leaves contact with the strip before asucceeding pair engages the strip, said work rolls being mounted in rollcages, said roll cages being geared to the respective rotating, drivenbacking rolls in such a ratio that each work roll, during its workingcycle, is backed by the same angular portion of the circumference of thebacking roll, said angular portion of the backing roll circumferencebeing profiled to produce a deviation ofthe working roll from a truecircular path during its working cycle.

8. A mill according to claim 7, wherein the ratio of the diameters ofthe backing roll to the work rolls is 2:1 and the gearing is such as toproduce a ratio of the speeds of the backing roll to the work roll cageof 3:1, and wherein each cage is provided with two work rolls and eachbacking roll is provided with two profiled portions.

9. A mill according to claim 7, wherein the ratio of the diameters ofthe backing roll to the work rolls is 2:1 and the gearing is such as toproduce a ratio of the speeds of the backing roll to the work roll cageof 3:1, and wherein each cage is provided with one work roll and eachbacking roll is provided with one profiled portion.

10. A mill according to claim 7, wherein the ratio of the diameters ofthe backing roll to the work rolls is 4:1 and the gearing is such as toproduce a ratio of the speeds of the backing roll to the work roll cageof 2.511, and having two work rolls in each cage, and four profiledportions on each backing roll.

11. A mill according to claim 7, wherein the ratio of the diameters ofthe backing roll to the work rolls is 4:1 and the gearing is such as toproduce a ratio of the speeds of the backing rolls to the work roll cageof 2.5:1, and having four work rolls in each cage, and eight profiledportions on each backing roll.

12. A mill according to claim 7, wherein the backing rolls and workrolls are of equal diameter, and the gearing is such as to produce aratio ofspeeds of the backing roll to the work roll cage of 4:1, andhaving siir work rolls in each cage and three profiled portions on eachbacking roll.

13. A mill according to claim 7, wherein the backing rolls and workrolls are of equal diameter, and the gearing is such as to produce aratio of speeds of the backing roll to the work roll cage of 4: l, andhaving four work rolls in each cage and one profiled portion on eachbacking roll,

14. A mill according to claim 7, in which edge retaining rollers aremounted on the periphery of the roll cages, each contacting one cornerof the roughly rectangular section of the workpiece in the roll bite.

1. The method of reducing vibrations in the operation of a planetarymill having rotating driven backing rolls and work rolls mounted incages, which includes the step of intermittently varying the angularvelocity of the driving means for said backing rolls in timed relationto the working cycle of the said work rolls, so as to reduce stresses insaid driving means near the end of each rolling cycle.
 2. The method ofclaim 1, wherein said variations in angular velocity are produced bycausing said work rolls to deviate from their circular paths and to moveparallel to each other during the final portion of the working cycle. 3.The method according to claim 2, wherein the deviation is produced bydriving the said roll cages at such a speed ratio with respect to thebacking rolls that each work roll, during its operating cycle, is backedby the same arc of the circumference of the backing roll, and profilingsaid arc to produce the required deviation.
 4. The method according toclaim 3, wherein said work rolls are also caused to deviate from theircircular paths near their point of engagement with the workpiece, toreduce the angle at which the work rolls meet the workpiece.
 5. Themethod according to claim 1, wherein said variation in angular velocityis produced by retarding the driving ends of the spindles during saidlast portion of the working cycle.
 6. The method according to claim 5,wherein said variation is produced by driving said backing rolls througha planetary reduction gear having a free element to oscillate insynchronism with the working cycles of the mill, so as further torelieve spindle stresses by retarding the driving ends of said spindlesin relation to their driven ends near the end of each working cycle. 7.A planetary rolling mill having a pair of backing rolls, and a number ofwork rolls symmetrically associated with each backing roll, the numberof work rolls associated with each backing roll being such that a givenpair of work rolls leaves contact with the strip before a succeedingpair engages the strip, said work rolls being mounted in roll cages,said roll cages being geared to the respective rotating, driven backingrolls in such a ratio that each work roll, during its working cycle, isbacked by the same angular portion of the circumference of the backingroll, said angular portion of the backing roll circumference beingprofiled to produce a deviation of the working roll from a true circularpath during its working cycle.
 8. A mill according to claim 7, whereinthe ratio of the diameters of the backing roll to the work rolls is 2:1and the gearing is such as to produce a ratio of the speeds of thebacking roll to the work roll cage of 3:1, and wherein each cage isprovided with two work rolls and each backing roll is provided with twoprofiled portions.
 9. A mill according to claim 7, wherein the ratio ofthe diameters of the backing roll to the work rolls is 2:1 and thegearing is such as to produce a ratio of the speeds of the backing rollto the work roll cage of 3:1, and wherein each cage is provided with onework roll and each backing roll is provided with one profileD portion.10. A mill according to claim 7, wherein the ratio of the diameters ofthe backing roll to the work rolls is 4:1 and the gearing is such as toproduce a ratio of the speeds of the backing roll to the work roll cageof 2.5:1, and having two work rolls in each cage, and four profiledportions on each backing roll.
 11. A mill according to claim 7, whereinthe ratio of the diameters of the backing roll to the work rolls is 4:1and the gearing is such as to produce a ratio of the speeds of thebacking rolls to the work roll cage of 2.5:1, and having four work rollsin each cage, and eight profiled portions on each backing roll.
 12. Amill according to claim 7, wherein the backing rolls and work rolls areof equal diameter, and the gearing is such as to produce a ratio ofspeeds of the backing roll to the work roll cage of 4:1, and having sixwork rolls in each cage and three profiled portions on each backingroll.
 13. A mill according to claim 7, wherein the backing rolls andwork rolls are of equal diameter, and the gearing is such as to producea ratio of speeds of the backing roll to the work roll cage of 4:1, andhaving four work rolls in each cage and one profiled portion on eachbacking roll.
 14. A mill according to claim 7, in which edge retainingrollers are mounted on the periphery of the roll cages, each contactingone corner of the roughly rectangular section of the workpiece in theroll bite.